var BASE64_MAPPING = [
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
    'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
    'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', '0', '1', '2', '3',
    '4', '5', '6', '7', '8', '9', '+', '/'
];

/**
 *ascii convert to binary
 */
var _toBinary = function (ascii) {
    var binary = new Array();
    while (ascii > 0) {
        var b = ascii % 2;
        ascii = Math.floor(ascii / 2);
        binary.push(b);
    }
    /*
     var len = binary.length;
     if(6-len > 0){
     for(var i = 6-len ; i > 0 ; --i){
     binary.push(0);
     }
     }*/
    binary.reverse();
    return binary;
};

/**
 *binary convert to decimal
 */
var _toDecimal = function (binary) {
    var dec = 0;
    var p = 0;
    for (var i = binary.length - 1; i >= 0; --i) {
        var b = binary[i];
        if (b == 1) {
            dec += Math.pow(2, p);
        }
        ++p;
    }
    return dec;
};

/**
 *unicode convert to utf-8
 */
var _toUTF8Binary = function (c, binaryArray) {
    var mustLen = (8 - (c + 1)) + ((c - 1) * 6);
    var fatLen = binaryArray.length;
    var diff = mustLen - fatLen;
    while (--diff >= 0) {
        binaryArray.unshift(0);
    }
    var binary = [];
    var _c = c;
    while (--_c >= 0) {
        binary.push(1);
    }
    binary.push(0);
    var i = 0, len = 8 - (c + 1);
    for (; i < len; ++i) {
        binary.push(binaryArray[i]);
    }

    for (var j = 0; j < c - 1; ++j) {
        binary.push(1);
        binary.push(0);
        var sum = 6;
        while (--sum >= 0) {
            binary.push(binaryArray[i++]);
        }
    }
    return binary;
};

/**
 *BASE64 Encode
 */
export function encodeBase64(str) {
    var base64_Index = [];
    var binaryArray = [];
    for (var i = 0, len = str.length; i < len; ++i) {
        var unicode = str.charCodeAt(i);
        var _tmpBinary = _toBinary(unicode);
        if (unicode < 0x80) {
            var _tmpdiff = 8 - _tmpBinary.length;
            while (--_tmpdiff >= 0) {
                _tmpBinary.unshift(0);
            }
            binaryArray = binaryArray.concat(_tmpBinary);
        } else if (unicode >= 0x80 && unicode <= 0x7FF) {
            binaryArray = binaryArray.concat(_toUTF8Binary(2, _tmpBinary));
        } else if (unicode >= 0x800 && unicode <= 0xFFFF) {//UTF-8 3byte
            binaryArray = binaryArray.concat(_toUTF8Binary(3, _tmpBinary));
        } else if (unicode >= 0x10000 && unicode <= 0x1FFFFF) {//UTF-8 4byte
            binaryArray = binaryArray.concat(_toUTF8Binary(4, _tmpBinary));
        } else if (unicode >= 0x200000 && unicode <= 0x3FFFFFF) {//UTF-8 5byte
            binaryArray = binaryArray.concat(_toUTF8Binary(5, _tmpBinary));
        } else if (unicode >= 4000000 && unicode <= 0x7FFFFFFF) {//UTF-8 6byte
            binaryArray = binaryArray.concat(_toUTF8Binary(6, _tmpBinary));
        }
    }

    var extra_Zero_Count = 0;
    for (var i = 0, len = binaryArray.length; i < len; i += 6) {
        var diff = (i + 6) - len;
        if (diff == 2) {
            extra_Zero_Count = 2;
        } else if (diff == 4) {
            extra_Zero_Count = 4;
        }
        //if(extra_Zero_Count > 0){
        //	len += extra_Zero_Count+1;
        //}
        var _tmpExtra_Zero_Count = extra_Zero_Count;
        while (--_tmpExtra_Zero_Count >= 0) {
            binaryArray.push(0);
        }
        base64_Index.push(_toDecimal(binaryArray.slice(i, i + 6)));
    }

    var base64 = '';
    for (var i = 0, len = base64_Index.length; i < len; ++i) {
        base64 += BASE64_MAPPING[base64_Index[i]];
    }

    for (var i = 0, len = extra_Zero_Count / 2; i < len; ++i) {
        base64 += '=';
    }
    return base64;
}

/**
 *BASE64  Decode for UTF-8
 */
export function decodeBase64(_base64Str) {
    var _len = _base64Str.length;
    var extra_Zero_Count = 0;
    /**
     *计算在进行BASE64编码的时候，补了几个0
     */
    if (_base64Str.charAt(_len - 1) == '=') {
        //alert(_base64Str.charAt(_len-1));
        //alert(_base64Str.charAt(_len-2));
        if (_base64Str.charAt(_len - 2) == '=') {//两个等号说明补了4个0
            extra_Zero_Count = 4;
            _base64Str = _base64Str.substring(0, _len - 2);
        } else {//一个等号说明补了2个0
            extra_Zero_Count = 2;
            _base64Str = _base64Str.substring(0, _len - 1);
        }
    }

    var binaryArray = [];
    for (var i = 0, len = _base64Str.length; i < len; ++i) {
        var c = _base64Str.charAt(i);
        for (var j = 0, size = BASE64_MAPPING.length; j < size; ++j) {
            if (c == BASE64_MAPPING[j]) {
                var _tmp = _toBinary(j);
                /*不足6位的补0*/
                var _tmpLen = _tmp.length;
                if (6 - _tmpLen > 0) {
                    for (var k = 6 - _tmpLen; k > 0; --k) {
                        _tmp.unshift(0);
                    }
                }
                binaryArray = binaryArray.concat(_tmp);
                break;
            }
        }
    }

    if (extra_Zero_Count > 0) {
        binaryArray = binaryArray.slice(0, binaryArray.length - extra_Zero_Count);
    }

    var unicode = [];
    var unicodeBinary = [];
    for (var i = 0, len = binaryArray.length; i < len;) {
        if (binaryArray[i] == 0) {
            unicode = unicode.concat(_toDecimal(binaryArray.slice(i, i + 8)));
            i += 8;
        } else {
            var sum = 0;
            while (i < len) {
                if (binaryArray[i] == 1) {
                    ++sum;
                } else {
                    break;
                }
                ++i;
            }
            unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 1, i + 8 - sum));
            i += 8 - sum;
            while (sum > 1) {
                unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 2, i + 8));
                i += 8;
                --sum;
            }
            unicode = unicode.concat(_toDecimal(unicodeBinary));
            unicodeBinary = [];
        }
    }
    let ret = '';
    for (let s of unicode) {
        ret += String.fromCharCode(s);
    }
    return ret;
}
//
// function test() {
//     if (encodeBase64('手动阀电视发送') != '5omL5Yqo6ZiA55S16KeG5Y+R6YCB') {
//         throw "base64 编码错误 " + encodeBase64('手动阀电视发送');
//     }
//     if (decodeBase64('5omL5Yqo6ZiA55S16KeG5Y+R6YCB') != '手动阀电视发送') {
//         throw "base64 解码错误 " + decodeBase64('5omL5Yqo6ZiA55S16KeG5Y+R6YCB');
//     }
//     console.log("测试Base64编码通过");
// }
//
// test();